1. Field of the Invention
This invention relates to electronic controls for an internal combustion engine.
2. Prior Art
In known production implementations, fuel delivery systems have typically used a mechanical fuel pressure regulator to control to a nominal fuel injection pressure. Fuel not ingested by the engine was returned to the fuel tank (see FIG. 1). With this type of fueling system, the instantaneous pressure across the fuel injectors (.DELTA.p.sub.inj) was not known exactly, nor was it adjustable during operation. Therefore, fueling calculation done in an electronic engine control may have used a fixed nominal curve relating the desired fuel to be injected (m.sub.inj) to a corresponding injection pulsewidth (PW.sub.inj) that tells the time the injector is to be commanded open. An example of this type of piece-wise linear fuel injector flow curve is shown in FIG. 2, at a fixed injection pressure.
Current production often modifies fuel injector pulsewidths, but strictly as a function of the desired fuel mass to be injected. There are also Hot Injector COMPensation (HICOMP) strategies, but these are ad hoc and may not use a fuel rail temperature sensor. Neither of these account or allow for varying injection pressures.